Biotechnological approaches to improve drought tolerance of Coffea arabica

Abstract

Overexpression of SHINE gene induces the expression of stress-related genes under normal growth conditions in transgenic plants and then confers increased tolerance to drought. In recent years, rapid procedures for obtaining transgenic roots have been developed using Agrobacterium rhizogenes, leading to the production of so-called “composite plants” comprising a transgenic root system attached to non-transformed shoot tissues. In Chapter II, it was determined the effect of overexpression of the Arabidopsis SHN2 gene in stable and/or chimeric transgenic Arabidopsis thaliana and Brassica rapa plants subjected to drought treatments. Chapter III was developed a rapid and efficient genetic transformation method via A. rhizogenes to create chimeric C. arabica (Catuaí Vermelho IAC 144) with wild-type shoots and transgenic roots, enabling the testing of potentially interesting genes in future stable transformations using A. tumefaciens or A. rhizogenes. In Chapter IV, roots overexpressing the SHN2 gene of Arabidopsis were transformed in transgenic hairy roots of coffee to improve the drought tolerance of such chimeric plants. 50 percent of the 35S::SHN2 chimeric transgenic Arabidopsis plants survived the water stress treatment and recovered after rewatering. In contrast, 42 percent of the coffee hypocotyls infected with A. rhizogenes carrying the pREDRoot plasmid had at least one root expected to be transformed, while those with the construct 35S::SHN2 had 32 percent transformation. In the drought experiment, the DsRED (control) chimeric coffee plants did not recover from the 15-day dehydration treatment and dried out all while the 35S::SHN2 chimeric plants recovered and became greener and stronger.